Using Analytics UserID or ClientID to ID leads reaching Salesforce

Has anyone used Google Analytics User ID and/or Client ID programming features to uniquely ID site visitors and especially to attach lead source information to lead forms sent to Salesforce? If so how well does it work for you, and is it difficult to program?

Client is interested in the potential for using Analytics User ID and Client ID to identify leads coming from AdWords so that AdWords-driven leads can be tracked in Salesforce.

Not familiar with how Salesforce forms are implemented, but a solution I've developed in the past is to grab UTM information on click, generate a formatted session token as the UserID, and pass that along with a form submission to track in our backend. That way, we can track the flow of users from AdWords in Analytics or via the API, such as:

campaign_adCTA_randomHash

Where campaign and adCTA are UTM values, and a random hash to identify this session.